The present invention is embodied in a method of and apparatus for extracting the "belly" of a marine mollusk, such as a clam, from the remainder of the clam meat after the clam has been shucked. The commercial necessity for de-bellying clams is thoroughly discussed in a number of prior United States patents, including the following patents which are made of record herein under 37 C.F.R. 1.56: U.S. Pat. Nos.:
______________________________________ 3,659,315 3,890,676 3,688,344 3,964,131 3,789,457 4,148,112 ______________________________________
In the patented and commercial prior art, clam bellies are removed by a variety of methods which result in varying degrees of damage to the usable meat causing it to lose some of its firmness and weight. Frequently, the clam bellies are separated from the meat by hand using physical pressure. A steam injection method of extraction is known in the prior art as well as a mechanical beating method. It is also known to soak and agitate the mollusks in tanks to loosen the bellies for easier separation by hand or by other prior art methods. All of these belly extracting processes result in serious damage to the usable clam meat and are outmoded and unacceptable under present-day commercial standards.
One fairly recent method of extracting clam bellies is disclosed in U.S. Pat. No. 3,688,344 to Carlson. This method essentially involves impacting whole clams at high velocity against a stationary screen panel which allows the bellies to pass through the screen and to be separated from the remainder of the clam body which is arrested in its movement by the screen. While the method is quite effective in separating the bellies from the clam meat, the meat is damaged in terms of loss of firmness and weight due to the escape of certain juices from the tissue.
In a more recent prior art method disclosed in U.S. Pat. No. 4,148,112 to Marvin, shucked whole clams are delivered by suction through a pipe or tube into a fluid shearing zone where the whole clams are subjected to the action of a very high velocity water stream passing through a venturi mechanism at right angles to the axis of the clam induction or infeed tube. The Marvin patent specifies that the high velocity fluid stream generates forces sufficient to shear the bellies from whole clams within the fluid shearing zone. The separated bellies and clam meat are then delivered at high velocity into a collection tank and from this tank are delivered onto a separating conveyor. While the Marvin patent purports to be an improvement on the impact clam extractor of Carlson in terms of lessening structural damage to the clam meat, it is believed that in practice the fluid shearing method of Marvin causes as much or more damage to the meat as the Carlson process. The Marvin patent, for example, specifies shearing fluid velocities in the range of 10,000-20,000 feet per minute at a pressure of 124 psi. While the Marvin method undoubtedly is effective in separating the bellies from the remainder of the clam meat, it is clear that the fluid velocities involved at the shearing zone are sufficient to badly damage the meat and rob it of its desirable firmness.
In light of the above, it is the object of this invention to improve on the prior art in general and on the Marvin method of belly extraction in particular by provision of an extraction method and apparatus which is much gentler in relation to the delicate clam meat and equally or more effective in cleanly separating bellies from the meat compared to Marvin or any other known prior art.
The improved results obtained through the invention are due to the utilization of fluid in the process at a greatly reduced velocity compared to Marvin where it impinges on the clams and the direction of the flushing fluid in two converging streams slightly downstream from the clam delivery pipe or tube, whereby the two fluid streams exert a firm but gentle squeezing force on the clams while flushing them through a pipe toward a decelerating head at the far end of the flush pipe where the clam meat is gently decelerated and directed onto a separating means where the meat and bellies can be separately collected. The use of a reduced velocity fluid stream in the method is enabled by employing a delivery tube for the whole clams upstream from the primary suction chamber which contains a plurality of bulbous zones or sections intervened by constrictions. In passing through this delivery tube under the influence of suction, the clams are subjected to multiple squeezing and multiple abrupt velocity changes which progressively loosens the bellies from the meat and eventually separates the bellies from the meat without any noticeable damage to the meat in terms of loss of firmness and weight. When the clams exit the delivery tube, the bellies are essentially separated from the undamaged meat and the total product is propelled through the flush tube by the flat converging fluid streams generated by nozzles preferably disposed slightly downstream from the exit end of the bulbous delivery tube. The converging streams trap each clam and exert a further squeezing force thereon within the flushing pipe and should there be any incompletely separated bellies when the clams exit the delivery tube, the extracting or separating process is completed within the flushing tube.